Fuel system



Patented June 2, 1953 UNITED S Tal" FUEL SYSTEM Floyd J. Boyer,Indianapolis,

General Motors Gerporation, corporation of Delaware Ind., assigner toDetroit, Mich., a

13 Glaims.

This invention has to do with fuel systems, particularly fuel systemsfor combustion gas turbines which are used to propel airplanes. Morespecifically, thc invention has to do with fuel systems which includetwo pumps of the same nominal capacity which are arranged in series andeach of which is capable of supplying by itself at the desired pressureall of the fuel it is desired to supply to the user.

The principal object of the invention is to provide a fuel system of thetype referred to in which, whether its actual `capacity is higher orlower than that of the other pump, a preselected one of the pumps willsupply all of the fuel to the user and the other pump will operate idlyas long as the actual capacity of the former exceeds a preselected valueand lupon decrease of the actual capacity of the former to a value belowthe preselected value the latter will supply all of the fuel to theuser. Decrease in the actual capacity of a pump to a value lbelow thepreselected value is hereinafter referred to as total failure of thepump.

Another object of the invention is to provide in a fuel system of thetype referred to means for indicating whether the individual fuel pumpsare operating below or above a preselected efficiency regardless ofwhich of the pumps is operating at the higher eiliciency.

For a better understanding of the objects and nature of this invention,reference is made to the following specification and the accompanyingdrawing wherein the preferred embodiment of the invention is describedand illustrated.

In the accompanying drawing:

Figure l illustrates more or less diagrammatically a fuel system for anairplane propelling combustion gas turbine in which the invention isembodied.

Figure 2 is an enlarged longitudinal section through a valve included inthe system shown in Figure l. l

In the drawing, the reference character le indicates the manifoldthrough which fuel is supplied to the several `burners of an airplanepropelling combustion gas turbine and the reference character II va pipein which fuel from a supply tank (which is not shown in the drawing) ismaintained by a pump (which is not `shown in the drawing). I from thepipe II, there are provided primary and secondary pumps l2 and it whichare of `the same nominal capacity and vare driven at the same speed bythe turbine and of which each is capable vby itself of supplying at thedesired To lsupply fuel to the manifold coil spring 35 which :bearsagainst the end 2 pressure all of the fuel it the turbine.

The pipe II is connected to the manifold I0 by pipes id, l5 and lli.Between sections of the pipe I5 there is interposed a filter I I yandbetween the pipes I5 and It there is interposed a control I il with anoperating lever 4l for regulating the rateat which fuel is supplied tothe manifold lo.

The inlet of the primary pump IZ is connected .by a pipe i@ to the pipesIl and I4 at their junction and the outlet thereof is connected by apipe 2li to the pipe Ill on the downstream side of its junction with thepipe II. Between sections of the pipe 2li there is interposed a fuellter 2l. In the pipe Ill between the junctions of the pipe I9 and 2litherewith, there is disposed a check valve 22 which is closed when thepressure on the outlet side of the primary pump I2 exceeds the pressureon the inlet side thereof.

The inlet of the secondary pump I3 is connected by a pipe 23' to thepipe I 4 on the downstream side of its junction with the pipe 20 and theoutlet thereof is connected by a pipe 24 to the pipes Il and I5 at theirjunction. In the pipe I l between the junctions of the pipes 23 and 2dtherewith, there is rdisposed a check valve 25 which is closed when thepressure on the outlet side of the secondary pump I3 exceeds thepressure on the inlet side thereof. The 'sections of the conduit I `Ilin which the check valves 22 and 25 are located constitute bypassconduits around the primary and secondary pumps I2 and I3 respectively.

The pipes 23 and '24 are interconnected by a 'second bypass pipe 26between sections of which there is interposed a bleed valve 2l. Thebleed valve includes a body 28 with an enlarged portion at one endwithin which there is a cham- ;ber 29 and a reduced portion at itsopposite end through which extends a bore 3D which opens into thechamber v29. The chamber 29 is connected to the section of the pipe 25which is connected to the pipe 2li and the bore 3B to the section of thepipe 26 which is connected to the pipe 23. In the bore 3B there 'isdisposed a piston valve 3i with an enlarged head 3'2 disposed in thechamber 29. Into the valve 3l to a point adjacent the enlarged head 32,there extends lengthwise of the valve a bore 33' and through the body ofthe valve adjacent theenlarged head 32, there extend transversely vofthe piston bores 31S which intersect the bore 33. In the bore Sil of thebody 28, there is disposed a is desired to supply to the valve 3l and anannular member 3B which is threaded into the bore and tends to maintainthe valve in a position in which the transverse Ibores 34 open into thechamber 29. In the chamber 29 there is disposed a plug-like mem ber 31which is threaded into the wall of the chamber and has on it a boss 58against which abuts a boss 49 on the enlarged head 32 of the valve 3l tolimit the extent to which the valve may be opened. Through the member 31there extend restricted bores 50 through which fuel may pass from theportion of the chamber 29 on the outer into the portion of the chamberon the inner side of the member. The extent to which the valve 3l may beopened may be varied by adjustment of the member 31 and the eiectiveresistance of the spring 35 to closing the valve may be varied byadjustment of the member 3B.

To the inlet and outlet of the secondary pump I3, there are connectedpressure responsive members 39 and 4B which are connected to a switch dIso that the switch closes a circuit from a source of electrical energy42 to a light d3 when the pressure on the outlet side of the secondarypump exceeds that on the inlet side thereof by a preselected value.

The control IS is of the type in which the fuel supplied to it in excessof that it is desired to supply to the manifold I is returned to theinlets of the fuel pumps. To return this fuel to the inlets of the fuelpumps there is provided a pipe 38 which is connected to the control andto the pipe III between its junction with the pipe II and the checkvalve 22.

When the turbine is operating, the primary pump I2 withdraws fuel fromthe pipe II through the pipe I9 and discharges it into the pipe I4through the pipe 20 and the lter 2I. If both of the pumps I2 and I3 areoperating at the same emciency or the primary pump I2 is operating athigher efficiency than the secondary pump I3, whether inherently or byreason of partial or total failure of the secondary pump, pressure ofthe fuel on the outlet side of the primary pump will keep the checkvalve 22 closed. Under these conditions fuel will be supplied by theprimary pump to the manifold III through the pipe 20, the section of thepipe I4 between the junctions of the pipes 20 and 23 therewith, the pipe23, the secondary pump I3, the pipes 2li and I5. the filter I1, thecontrol I8 and the pipe I6. The excess, if any, of fuel supplied by theprimary pump over that forwarded by the secondary pump passes directlyinto the pipe I through the section of the` pipe I4 between thejunctions of the pipes 23 and 24 therewith. Under the conditionsunderconsideration the secondary pumps of course, operates idly.

If the secondary pump I3 is operating at higher efficiency than theprimary pump I2, whether inherently or by reason of failure, short ofsubstantially total failure, of the primary pump, the primary pump willcontinue to operate as described above. The members 36 and 31 of thevalve 21 are, however, so adjusted that until the primary pump hasfailed substantially totally the valve 21 remains open and fuel isby-passed through the pipe 28 and the valve 21 from the outlet to theinlet side of the secondary pump at a rate substantially equal to thedifference between the capacities of the secondary and primary pumps sothat the secondary pump continues to operate idly. The valve 21 thusserves when the secondary pump is operating at higher efdciency than theprimary pump to maintain the differential between the pressures on theoutlet and inlet sides of the secondary pump below the preselected valueat which the switch "II is closed and idle operation of the secondarypump until the primary pump has failed substantially totally. Uponsubstantially total failure of the primary pump, the differentialbetween the pressures on the outlet and inlet sides of the secondarypump increases to a value above the preselected value at which theswitch 4I is closed. Consequently, an unlighted condition of the lighti3 indicates that the primary pump has not failed substantially totallyand a lighted condition of the light indicates that the primary pump hasfailed substantially totally.

The increase in the differential between the pressures on the outlet andinlet sides of the secondary pump which occurs when the primary pump I2fails substantially totally causes the valve 21 to close and thesecondary pump I3, consequently to take the full load of supplying fuelto the control I8 at the desired rate and pressure. Under thiscondition, the check valve 22 is open and the check valve 25 is closed,as it is whenever the secondary pump is operating at a higher eiiciencythan the primary pump, and fuel is supplied from the pipe II directly tothe inlet of the secondary pump through the pipes I4 and 23. Under thiscondition some fuel may also be supplied to the inlet of the secondarypump by the primary pump unless the primary pump has absolutely totallyfailed. The restriction of the bores 5B in the member 31 results inincrease of the fuel pressure on the Valve l31 in the direction to closethe valve as the valve is closed and, consequently, upon substantiallytotal failure of the primary pump, the valve 3i immediately closescompletely and remains completely closed.

To afford a check on the operation of the secondary pump1 there isprovided means by which, in effect, the primary pump may be put out ofoperation. This-means includes a by-pass in the form of a pipe 44 fromthe outlet to the inlet side of the primary pump and between sections ofthe pipe a solenoid operated valve l5 which normally closes the pipe butmay be opened by closing a switch 46 in a circuit from the source ofelectrical energy 42 to the solenoid. When the valve 45 is open alighted condition of the light 43 indicates that the secondary pump hasnot failed and an unlighted condition of the light 133 indicates thatthe secondary pump has failed Sub stantially totally.

To afford an indication of the sense in which the term substantiallytotal failure is used in this specification, it may be well to add that,assuming that the primary and secondary pumps are individually nominallycapable of supplying fuel at twice the maximum rate it is desired tosupply fuel to the user, a reduction of the capacity of a pump to, say.of its nominal capacity may be considered a substantially total failureof the pump.

l'. claim:

l. In a system for advancing fuel from a reservoir to a user, a linethrough which fuel may be conducted from the reservoir to the user, twopumps in series in the line for advancing fuel through the line from thereservoir to the user, a line through which fuel may be conducted aroundeach of the pumps from its inlet to its outlet, a valve in each of thelast specified lines which inhibits flow of fuel therethroughfrom the`outlet to the inlet of the pump around which the line E the outlet tothe inlet of the secondary pump in excess of a predetermined rate.

9. A fluid pumping system comprising a primary pump and a secondary pumpconnected in series, the pumps being of the positive-displacement typeand of substantially equal capacity, a bypass conduit around each pump,a check valve in each bypass conduit to prevent flow from the outlet tothe inlet of the corresponding pump, a second bypass conduit around thesecondary pump, a normally open valve in the second bypass conduit, andmeans responsive to a predetermined rate of ilovv through the secondbypass between the outlet and the inlet of the secondary pump to closethe normally open valve.

10. A fluid pumping system comprising a primary pump and a secondarypump connected in series, a bypass conduit around each pump, a checkvalve in each bypass conduit to prevent flow from the outlet to theinlet of the co1'- responding pump, a second bypass conduit around thesecondary pump, a normally open valve in the second bypass conduit, andmeans responsive to a pressure diierential between the outlet and theinlet of the secondary pump to close the normally open valve.

11. A fluid pumping system comprising a primary pump and a secondarypump connected in series, the pumps being of the positive-displacementtype and of substantially equal capacity, a bypass conduit around eachpump, a check valve in each bypass conduit to prevent flow from theoutlet to the inlet of the corresponding pump, a second bypass conduitaround the secondary pump, a normally open valve in the second bypassconduit, and means responsive to a pressure differential between theoutlet and the inlet of the secondary pump to close the normally openvalve.

12. A uid pumping system comprising a primary pump and a secondary pumpconnected in series, the pumps being of the positive-displacement typeand of substantially equal capacity, a bypass conduit around each pump,a check valve in each bypass conduit to prevent W from the outlet to theinlet of the corresponding pump, a second bypass conduit around thesecondary pump, a normally open valve in the second bypass conduit,means responsive to a pressure differential between the outlet and theinlet of the secondary pump to close the normally open valve, a third bypass conduit around the primary pump, and a normally closed stop valvein the third bypass conduit.

13. In combination, two pumps driven in synchronism, the pumps beingnormally connected in series, means responsive to normal operation ofone pump to unload the other pump, means responsive to diminished outputvolume of the said one pump to activate the said other pump and bypassthe said one pump, and means for diverting at least part of the outputof the said one pump to check the operation of the said activating meansand the said other pump.

FLOYD J. BOYER.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 615,760 Smith Dec. 13, 1898 1,049,894 Merrill Jan. 7, 19131,477,850 Pool Dec. 18, 1923 1,814,857 Rosle July 14, 1931 1,825,661Gull Oct. 6, 1931 2,218,565 Vickers Oct. 22, 1940 2,366,388 Crosby Jan.2, 1945

